Transistorized ignition system for internal combustion engines



Oct. 4, 1966 N. A. JUKES ETAL 3,277,340

TRANSISTORIZED IGNITON SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Dec. 5, 1965 s Sheets-Sheet 1 ac SOURCE.

Oct. 4, 1966 N. A. JUKES ETAL 3,277,340

TRANSISTORIZED IGNITON SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Dec. 5, 1963 5 Sheets-Sheet 2 /f/ll Oct. 4, 1966 N. A. J KEs ETAL 3,277,340

TRANSISTORIZED IGNITON SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Dec. 5, 1963 5 Sheets-Sheet 3 United States Patent Ofifice Patented Oct. 4, 1966 3 277,340 TRANSISTORIZED IGNITION SYSTEM FOR IN- TERNAL COMBUSTION ENGINES Norman Alfred Jukes, Walsail, and John Kenneth Jenkinson, West Heath, Birmingham, England, assignors to Joseph Lucas (Industries) Limited, Birmingham, England Filed Dec. 3, 1963, Ser. No. 327,661 Claims priority, application Great Britain, Dec. 5, 1962, 45,985/ 62 7 Claims. (Cl. 315-214) This invention relates to spark ignition apparatus for internal combustion engines.

Spark ignition apparatus according to the invention comprises a spark generating circuit for supplying sparks to the plugs of the engine in turn, a trigger circuit which when biased by an input permits the spark generating circuit to produce a spark, an oscillator providing the biasing input to the trigger circuit, and magnetic means driven by the engine for preventing the oscillator from providing said biasing input except when a spark is required.

The oscillator may be permanently connected to the trigger circuit, in which case the magnetic means only permits the oscillator, to oscillate when a spark is required. Alternatively, however, the oscillator may be continuously operating, in which case the magnetic means de-couples the oscillator from the trigger circuit except when a spark is required.

In the accompanying drawings:

FIGURE 1 is a circuit diagram illustrating one example of the invention;

FIGURES 2 and 3 respectively are sketches at right angles to one another illustrating the magnetic means for controlling the oscillator;

FIGURE 4 is a sectional side view illustrating a practical arrangement of the magnetic means for controlling the oscillator combined with a conventional engine distributor;

FIGURE 5 is a sectional end view of FIGURE 4;

FIGURE 6 is a sketch similar to FIGURE 3 illustrating a modification;

FIGURE 7 is a sketch similar to FIGURE 3 illustrating a further modification;

FIGURE 8 is a diagram illustrating part of the circuit corresponding to FIGURE 7;

FIGURE 9 illustrates a further modification of part of the circuit shown in FIGURE 1;

FIGURE 10 illustrates a modification of FIGURE 8;

FIGURES 11 and 12 respectively are sketches illustrating modifications of the. arrangement shown in FIG- URE 7;

FIGURE 13 shows a practical version of FIGURE 11;

FIGURE 14 is a circuit diagram illustrating a modified version of FIGURE 1, and

FIGURE 15 illustrates a modification of FIGURE 1 which is also applicable to the other circuit diagrams.

Referring to FIGURE 1, there are provided first and second terminals 21, 22 which in use are connected to a battery or other D.C. source 23 so as to be of positive and negative polarities respectively. There is further provided a first transformer 24 having one end of its primary winding 25 connected to the terminal 21, and the other end of its winding 25 connected to the collector of an n.p.n. type transistor 26. The emitter of this transistor 26 is connected to the terminal 22 through a resistor 27, whilst its base is connected to one end of the secondary winding 28 of the transformer, the other end of the winding 28 being connected to the terminal 21 through a resistor 29 having a capacitor 31 in parallel therewith.

There is further provided a transformer 32 having one end of its primary winding 33 connected through a resistor 34 to the terminal 21, and the other end of its Winding 33 connected to the collector of an n.p.n type transistor 35, the emitter of which is connected to the terminal 22. The base of the transistor 35 is connected to the emitter of the transistor 26 through the secondary winding 36 of the transformer 32.

The collector of the transistor 35 is connected to the cathode of a diode 37, the anode of which is connected to the terminal 21 through a resistor 38. Moreover, the

. anode of the diode 37 is connected through the anodes and cathodes of diodes 39, 41 in series to the base of an n.p.n type transistor 42. The base of the transistor 42 is further connected to the terminal 22 through :a resistor 43, whilst its emitter is connected to the terminal 22, and its collector is connected to the terminal 21 through the primary winding 44 of an ignition transformer 45.

The secondary winding 46 of the ignition transformer 45 is connected through a distributor 47 driven by the engine to the spark plugs 48 of the engine in turn.

The transformers 32, 45 are wound on cores so that their windings are permanently connected magnetically. However, the magnetic circuit of the transformer 24 comprises, as shown in FIGURES 2 and 3, an open rectangular core 49 which is split along one of its long sides. The windings 25, 28 are wound on the limbs on opposite sides of the split in the core, and the arrangement is such that the air gap between the windings is sufficient to couple them magnetically. Rotatable about an axis parallel to one of the longer sides of the core is a disc 51 which is driven by, and at a speed dependent on, the speed of the engine with which the ignition circuit is associated. Conveniently, the disc 51 is driven by the distributor shaft. The disc includes four slots 52 which extend inwardly towards the centre of the disc from the circumference thereof, and are mutually at right angles. The disc is rotated so that it passes between the windings 25, 28 and the arrangement is such that when a slot 52 is aligned with the two portions of the broken limb on which the windings 25, 28 are wound, the windings are coupled magnetically; at other times the windings 25, 28 are not coupled magnetically. The disc described is suitable for use with a four cylinder engine, and in other cases the number of slots will be equal to the number of cylinders. Moreover, the disc 51 could be driven indirectly by the engine through step-up or step-down gearing, in which case the number of slots could be a fraction of, or a multiple of, the number of engine cylinders.

The disc 51 is formed from conductive material, and the arrangement is such that when a solid part of the disc is between the windings of the transformer 24, the eddy currents flowing in the disc are suflicient to prevent oscillations of the circuit including the transformer 24 and the transistor 26. A small current flows through the collector and emitter of the transistor 26, but the transistor 35 is nonconductive. Moreover, current flowing through the resistor 38 and the diodes 39, 41 in series maintains the transistor 42 conductive, so that current fiows in the primary winding 44 of the ignition transformer 45.

When one of the slots 52 appears between the windings 25, 28 the circuit including the transformer 24, the resistor 29, capacitor 28 and the transistor 26 oscillates in known manner to produce an AC. voltage across the resistor 27. The first effect of this voltage will be to render the transistor 35 conductive. When the transis tor 35 conducts, current flowing through the resistor 38 can flow through the diode 37 and the collector and emitter of the transistor 35, so that the transistor 42 is cut off. Cutting off of the transistor 42 causes a high voltage to be developed in the secondary winding 46 of the ignition transformer, and a spark is applied to one of the plugs 48.

The transformer 32 causes the current in the transistor 35 to build up by regenerative action between its collector and base until saturation is reached, at which point the transistor 35 is switched off and the transistor 42 is switched on again. At this stage, if the transistor 26 and its associated components are still oscillating, a further spark will be produced. Thus, at speeds below a predetermined value more than one spark will be applied to each plug. However, if, by the time the transistor 35 becomes nonconductive, the transistor 26 and its associated components have ceased to oscillate, only a single spark will be applied to each plug 48.

FIGURES 2 and 3 illustrate the magnetic means for controlling the oscillator diagrammatically, but a practical arrangement is shown in FIGURES 4 and combined with a conventional distributor in place of the normal contact breaker. Referring to FIGURES 4 and 5, there is provided a hollow casing 53 within which is rotatably mounted a shaft 54 driven by the engine. Part of the shaft within the casing is surrounded by and in driving engagement with a sleeve 55, the sleeve being of increased cross-section at one end and in' driving engagement with an insulating member 56 which carries a rotor arm 57 extending radially relative to the shaft 54. At its inner end, the rotor arm 57 is in contact with a connector 58 which is connected to winding 46 of the ignition transformer 45, and at its outer end the arm terminates in conventional manner in a circumferentially extending arcuate portion (not seen in FIGURE 4) which as the shaft rotates comes into close contact with four contact pieces 59 connected to the engine spark plugs 48 respectively, so that current can flow through the rotor arm 57 to the plugs.

Secured to the casing 53 is a plate 61 which as shown in FIGURE 5 extends around part of the shaft 54. The plate 61 carries a pivot 62 on which is journalled an angularly movable link having a pair of arms 63, 64 extending arcuately on opposite sides of the shaft 54. The arm 63 carries at its extremity a housing 65 in which is mounted the core 49 of the oscillator. The disc 51 is replaced by a drum 66 which is secured to the sleeve 55 so as to rotate therewith. The drum 66 is slotted so that when a slot passes between the broken limb of the core 49 power is supplied through the ignition transformer 45 to the rotor arm 57, and the drum 66 is positioned relative to the rotor shaft in a manner to ensure that the rotor arm will always be in electrical communication with a spark plug when the oscillator operates.

Terminals 67 are provided on the casing 53, and provision is made in the casing for accommodating leads extending between the terminals 67 and the windings on the core 49. Three terminals are required for making the required connections to the windings 25, 28, the end of the winding which is connected to terminal 21 being earthed in any convenient manner. In order to accommodate the leads extending between the terminals 67 and the windings 25, 28, the .arm 63 is slotted to receive the leads and a part 68 is secured to the plate 61 to define therewith a terminal through which the leads extend.

A standard centrifugal advance mechanism 69 is incorporated for moving the sleeve 55 and insulating member 56 angularly. Further control of timing is provided by a known mechanism 71 which is responsive to the pressure in the air inlet of the engine, this mechanism controlling the angular position of the arms 63, 64. Although the arm 63 moves angularly about the pivot 62 and the drum 66 moves angularly about the shaft 54, suflicient clearance is provided to enable the mechanism to operate satisfactorily.

If desired, the air gap may be of such a size that oscillations are prevented from occurring. In this case, as shown in FIGURE 6, the core 49 may be U-shaped and the disc 51 is replaced by a spider including four magnetic arms 72 which permit oscillations when they pass over the limbs on which the windings 25, 28 are wound.

FIGURE 7 illustrates a modification in which the windings 25, 28 are wound on the same limb of the core 49 so that they oscillate at all times. However, the oscillatory circuit is coupled to the remainder of the circuit only when required. For this purpose the other limb of the core carries a winding 70 which is coupled to the oscillatory circuit either by a slotted disc 51 as shown in FIGURE 2, or 'by a spider having arms 72 as shown in FIGURE 7. The circuit for this arrangement is modified compared with FIGURE 1 as shown in FIGURE 8. As will be seen, the resistor 27 and the connection of the emitter of the transistor 26 to the winding 36 are omitted. The emitter of the transistor 26 is connected directly to the terminal 22, and moreover the resistor 29 and capacitor 31 in parallel may be connected between the winding 28 and the base of the transistor 26, instead of between the winding 28 and the terminal 21. The winding 70 has one end connected to the terminal 22, and its other end connected through the winding 36 to the base of the transistor 35.

In the modification of FIGURE 1 shown in FIGURE 9, the transistor 26 is replaced by a p-n-p transistor 73. In this case, the transistor 73 has its emitter connected to the terminal 21 and its collector connected to the terminal 22 through a resistor 74 in series with the winding 25. The base of the transistor 73 is connected to the terminal 22 through the resistor 29 in series with the winding 28, the resistor 29 being bridged by the capacitor 31 as before. A point intermediate the resistor 74 and the winding 25 is connected through the winding 36 to the base of the transistor 35. This circuit, which operates in the same way as FIGURE 1, is particularly useful where the negative terminal of the source 23 is to be earthed.

The circuit shown in FIGURE 8 can also be modified to employ a p-n-p transistor instead of the transistor 26. Refering to FIGURE 10, a p-n-p transistor 75 is shown with its base connected to the terminal 22; in this case the emitter of the transistor 75 is connected to the terminal 21 through the winding 28 and the parallel connection of the resistor 29 and the capacitor 31. The primary winding 25 is connected between the collector of the transistor 75 and the terminal 21. The operation is similar to that of the circuit shown in FIGURE 8.

The arrangement illustrated by FIGURES 7, 8 and 10 is not entirely satisfactory because it is difficult to construct a satisfactory oscillator on one limb of a core, and moreover there is a certain amount of leakage between the oscillator windings and the pick-up winding. In order to overcome this difliculty, the oscillator windings are removed from the core 49. The pick-up winding 70 is wound on one limb of the core 49 as before, and the output from the oscillator is fed through two additional windings connected in series with each other and with the winding 25, the additional windings being wound on the core 49. Magnetic means are provided as before, and the disposition and size of the additional windings are such that when no spark is required the voltages developed in the pick-up winding 70 by the additional windings cancel out. However, when a spark is required the balance is upset by the magnetic means.

Numerous arrangements are possible, but in one example shown in FIGURE 11 the core 49 is E-shaped with the pick-up coil 70 on its middle limb and equal additional windings 76, 77 connected in series and wound on the outer limbs. A magnetic arm 72 driven by the engine passes over the middle limb and one of the outer limbs to upset the balance when a spark is required. In the example shown in FIGURE 12, a two-limbed core 49 is used with the winding 76 on one limb and the other winding 77 and the pick-up winding 70 on the other limb.

'5 The additional windings 76, 77 will not in this case be equal; balance is upset by a magnetic arm 72 passing over the two limbs.

The magnetic material used for the cores and arms must have negligible eddy current loss and low reluctance; soft ferrites have been found to be satisfactory.

A further improvement can be obtained by tuning the pickup coil 70 to the oscillator frequency. Moreover, although in the examples described the output from the oscillator is fed to two additional windings in series, a similar effect can be obtained by feeding the oscillator output through a single winding and employing two pickup windings connected in opposition.

The circuit shown in FIGURE 11 is in practice difficult to balance owing to manufacturing tolerances and the arrangement shown in FIGURE 13 is preferred. This arrangement can be combined with a conventional distributor, and includes the core 49 carried by a housing 121 mounted on a nonrotatable part 122 of the distributor. The core carries the windings 70, 76, 77 and the arms 72 are constituted by ferrite rods 123 carried by a part 124 rotatable with the distributor shaft. The core 49 is deliberately made out of balance, and an exact balance is achieved by means of an adjustable ferrite rod 125 carried by the housing 121 and movable towards and away from the limb carrying the winding 76.

In all the circuit diagrams so far described, two blocking oscillators are used. The first oscillator which includes the transistor 26 (FIGURES 1 and 8) or 73 (FIG- URE 9) or 75 (FIGURE is operated by magnetic means driven by the engine, and in turn operates the second oscillator, which in each case includes the transistor 35 and provides a signal to an ignition transformer 45. The circuit now to be described is a modification of FIG- URE 1 in which a single transistor is employed in both oscillators.

Referring to FIGURE 14 there are provided first and second terminals 81, 82 for connection to a DC. source so as to be positive and negative in use respectively. The terminal 81 is connected through a resistor 83 and a capacitor 84 in parallel to one end of a secondary winding 85 of a first transformer 86, the winding 85 being bridged by a resistor 87. A variable point on the resistor 87 is connected through the anode and cathode of a diode 88 to the base of an-n-p-n transistor 89 having its emitter connected to the terminal 82, its base connected to the terminal 82 through a resistor 91, and its collector connected to the terminal 82 through the cathode and anode of a Zener diode 92.

The collector of the transistor 89 is further connected to the terminal 81 through the primary winding 93 of a second transformer 94, the winding 93 being bridged by a series circuit including a resistor 95 and the primary winding 96 of the transformer 86. The secondary winding 97 of the transformer 94 has one end connected to the terminal 82 and its other end connected through the anode and cathode of a diode 98 to the base of the transistor 89.

The circuit further incorporates an n-p-n transistor 99 having its emitter connected to the terminal 82 and its base connected to the terminal 82 through a resistor 101. The base is further connected through the cathode and anode of a diode 102 to the cathode of a diode 103 having its anode connected to the terminal 81 through a resistor 104 and to the collector of the transistor 89 through the anode and cathode of a diode 105. The collector of the transistor 99 is connected to the terminal 81 through a resistor 106 in series with the primary winding 107 of an ignition transformer 108, the secondary winding 109 of which is connected in use thnough a distributor (not shown) to the spark plugs of the engine in turn.

As before, magnetic means driven by the engine serve to couple the windings 85, 96 when a spark is required to permit the blocking oscillator constituted by the transformer 86 and the transistor 89 to oscillate by virtue of the feedback between the collector and base of the transistor 89 through transformer 94; the circuit values are such that these oscillations do not drive the transistor 89 to saturation, and so although part of the current flowing through the resistor 104 is diverted through the transistor 89, sufficient current flows through the base and emitter of the transistor 99 to hold it conductive.

At a predetermined amplitude, the oscillations in the transformer 86 operate the blocking oscillator constituted by the transformer 94 and the transistor 89, and the arrangement is such that the transistor 89 saturates and so short-circuits the base-emitter circuit of the transistor 99. The fall in flux in the ignition transformer 108 now produces a spark at a plug. At low speeds, the transformer 86 may still be magnetically coupled after produc tion of a spark, and in this case more than one spark will be supplied to each plug.

In all the examples so far described, a transistor (42 or 99) is connected in series with the primary winding of an ignition transformer. However, the transistor could be replaced by a switchable rectifier, which is a device similar to a controlled rectifier but having the additional property that it can be switched off by pulses applied to its gate. The use of a switchable rectifier simplifies the circuit, because the only connection necessary between the second transformer (32 or 94) and the switchable rectifier is an additional winding on the second transformer having one end connected to the negative terminal and the other end to the gate of the switchable rectifier. FIGURE 15 illustrates the arrangement as applied to FIGURE 1. The additional winding 111 has one end connected to the terminal 22 and its other end connected to the gate of the switchable rectifier 112; the cathode of rectifier 112 is connected to the terminal 22 and its anode is connected to the winding 44 through a resistor 113. A negative pulse is applied to the gate when the transistor 35 conducts, and a positive pulse is applied to the gate when the voltages in the transformer windings of transformer 32 reverse as a result of saturation of the transistor 35. The reverse voltage across the windings is preferably limited by a resistor and a diode (not shown) connected in series across the winding 33.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

1. Spark ignition apparatus for an internal combustion engine, comprising a spark generating circuit for supplying sparks to the plugs of the engine in turn, trigger circuit means connected to said spark generating circuit, normally occupying one position, but which when biased by an input assumes a second position in which it permits the spark generating circuit to produce a spark, a continuously operating fixed-frequency oscillator for providing the biasing input to said trigger circuit means, magnetic means driven by the engine for coupling said oscillator to said trigger circuit means when a spark is required and said trigger circuit means returning to said one position independently of said oscillator.

2. Spark ignition apparatus as claimed in claim 1 and further comprising a distributor in said spark generating circuit, said distributor including a shaft, and said magnetic means being housed within said distributor and driven by said shaft.

3. Spark ignition apparatus as claimed in claim 1 in which said magnetic means comprises a core, a pair of windings wound in series on said core, a pickup winding on said core for connecting said oscillator to said trigger circuit means whereby when no spark is required the voltages developed in the pick-up winding cancel out, but

when a spark is required, the balance is upset and a voltage is induced in said pick-up winding.

4. Spark ignition apparatus as claimed in claim 3 in which said core is normally out of balance and including adjust-able magnetic means for balancing said core.

5. Spark ignition apparatus as claimed in claim 3 in which said pick-up winding is tuned to the frequency of said oscillator.

6. Spark ignition apparatus for an internal combustion engine comprising a spark generating circuit for supplying sparks to the plugs of the engine in turn, trigger circuit means connected to said spark generating circuit and which when biased by an input permits said spark generating circuit to produce a spark, a continuously operating fixed-frequency oscillator for providing the biasing input to said trigger circuit means, magnetic means driven by the engine for preventing said oscillator from providing said bias input except when a spark is required, said fixed frequency oscillator being constituted by a blocking oscillator having a transistor with base and collector circuits forming part thereof with transformer windings in the base and collector circuits of said transistor, and said trigger circuit means being constituted by a second blocking oscillator comprising a transformer thaving windings in the collector and base circuits of said transistor used in said fixed frequency oscillator, the arrangement being such that the first-mentioned blocking oscillator alone does not saturate said transistor, but said transistor becomes saturated when the second blocking oscillator operates.

7. Spark ignition apparatus for an internal combustion engine, having at least one spark plug, comprising a spark generating circuit for intermittently supplying sparks, a trigger circuit means connected to said spark generating circuit, normally occupying one position but which when biased by an input assumes a second position which permits the spark generating circuit to produce a spark, a continuously operable fixed-frequency oscillator, for providing the bias input to said trigger circuit means, a pickup winding tuned to the frequency of said oscillator, magnetic means driven by the engine for coupling said oscillator to said trigger circuit means via said pick-up winding each time a spark is required for combustion and said trigger circuit means returning to said one position independently of said oscillator.

References Cited by the Examiner UNITED STATES PATENTS 2,898,392 8/1959 Jaesohke.

2,910,622 10/1959 McNultz 315-183 2,940,013 6/1960 Cook.

2,953,719 9/1960 Guiot 315-171 3,060,346 10/1962 'Sohner 123-148 3,152,281 10/1964 Robbins 315209 3,161,803 12/1964 Knittweiss.

3,175,123 3/1965 Dilger.

3,219,877 11/1965 Konopa 315-209 FOREIGN PATENTS 928,292 6/1963 Great Britain.

JOHN W. HUCKERT, Primary Examiner.

DAVID J. GALVIN, Examiner.

D. E. PICHINIK, M. EDLOW, Assistant Examiners. 

6. SPARK IGNITION APPARATUS FOR AN INTERNAL COMBUSTION ENGINE COMPRISING A SPARK GENERATING CIRCUIT FOR SUPPLYING SPARKS TO THE PLUGS OF THE ENGINE IN TURN, TRIGGER CIRCUIT MEANS CONNECTED TO SAID SPARK GENERATING CIRCUIT AND WHICH WHEN BIASED BY AN INPUT PERMITS SAID SPARK GENERATING CIRCUIT TO PRODUCE A SPARK, A CONTINUOUSLY OPERATING FIXED-FREQUENCY OSCILLATOR FOR PROVIDING THE BIASING INPUT TO SAID TRIGGER CIRCUIT MEANS, MAGNETIC MEANS DRIVEN BY THE ENGINE FOR PREVENTING SAID OSCILLATOR FROM PROVIDING SAID BIAS INPUT EXCEPT WHEN A SPARK IS REQUIRED, SAID FIXED FREQUENCY OSCILLATOR BEING CONSTITUTED BY A BLOCKING OSCILLATOR HAVING A TRANSISTOR WITH BASE AND COLLECTOR CIRCUITS FORMING PART THEREOF WITH TRANSFORMER WINDINGS IN THE BASE AND COLLECTOR CIRCUITS OF SAID TRANSISTOR, AND SAID TRIGGER CIRCUIT MEANS BEING CONSTITUTED BY A SECOND BLOCKING OSCILLATOR COMPRISING A TRANSFORMER HAVING WINDINGS IN THE COLLECTOR AND BASE CIRCUITS OF SAID TRANSISTOR USED IN SAID FIXED FREQUENCY OSCILLATOR, THE ARRANGEMENT BEING SUCH THAT THE FIRST-MENTIONED BLOCKING OSCILLATOR ALONE DOES NOT STATURATE SAID TRANSISTOR, BUT SAID TRANSISTOR BECOMES SATURATED WHEN THE SECOND BLOCKING OSCILLATOR OPERATES.
 7. SPARK IGNITION APPARATUS FOR AN INTERNAL COMBUSTION ENGINE, HAVING AT LEAST ONE SPARK PLUG, COMPRISING A SPARK GENERATING CIRCUIT FOR INTERMITTENTLY SUPPLYING SPARKS, A TRIGGER CIRCUIT MEANS CONNECTED TO SAID SPARK GENERATING CIRCUIT, NORMALLY OCCUPYING ONE POSITION BUT WHICH WHEN BIASED BY AN INPUT ASSUMES A SECOND POSITION WHICH PERMITS THE SPARK GENERATING CIRCUIT TO PRODUCE A SPARK, A CONTINUOUSLY OPERABLE FIXED-FREQUENCY OSCILLATOR, FOR PROVIDING THE BIAS INPUT TO SAID TRIGGER CIRCUIT MEANS, A PICKUP WINDING TUNED TO THE FREQUENCY OF SAID OSCILLATOR, MAGNETIC MEANS DRIVEN TO THE ENGINE FOR COUPLING SAID OSCILLATOR TO SAID TRIGGER CIRCUIT MEANS VIA SAID PICK-UP WINDING EACH TIME A SPARK IS REQUIRED FOR COMBUSTION AND SAID TRIGGER CIRCUIT MEANS RETURNING TO SAID ONE POSITION INDEPENDENTLY OF SAID OSCILLATOR. 